In "The Child", Guinan tells Wesley that she never met Picard before coming aboard the Enterprise. Yet this episode establishes that she met Picard centuries before her arrival on the ship. While Guinan would undoubtedly want to protect the timeline by not revealing details of this meeting, it doesn't seem like her to tell such a direct lie.

Also, why does Geordi openly wear his VISOR whilst wandering the 19th century hospital where locals can see him?

Great Moment :

Sam Clemens walking the halls of the Enterprise-D and finding out about life in the 24th century.

Body Count :

Several aliens in the cave, at least one Human on Earth.

Factoid :

Although this two parter was the first time that Jerry Hardin had played Sam Clemens, he became so fond of the role that he created a one man touring show based on him.

Plotline

Undercover in the past, the Enterprise crew must fight the aliens while avoiding awkward questions from none other than Mark Twain.